Gene Therapy Shows Promise in Factor IX Coagulant Activity for Hemophilia B

Reduction in annualized bleeding rate and in factor use with infusion of viral vector with transgene
Reduction in annualized bleeding rate and in factor use with infusion of viral vector with transgene

HealthDay News — For men with hemophilia B who have factor IX coagulant activity of 2% or less of normal value, infusion of a single-stranded adeno-associated viral (AAV) vector with factor IX Padua transgene is associated with a reduction in annualized bleeding rate, and in factor use, according to a study published in the December 7 issue of the New England Journal of Medicine.

Lindsey A. George, MD, from the Children's Hospital of Philadelphia, and colleagues infused a single-stranded AAV vector consisting of a bioengineered capsid, liver-specific promoter, and factor IX Padua transgene in 10 men with hemophilia B who had factor IX coagulant activity of 2% or less of normal value. 

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The researchers found noted no serious adverse events during or after vector infusion. In all participants, vector-derived factor IX coagulant activity was sustained, with a mean steady-state factor IX coagulant activity of 33.7 ± 18.5%. The annualized bleeding rate was significantly reduced on cumulative follow-up of 492 weeks among all participants (range of follow-up, 28 to 78 weeks) (mean rate, 11.1 events per year before vector admission versus 0.4 events per year after administration; P=0.02); factor use also decreased (mean dose, 2,908 IU/kg before vector administration versus 49.3 IU/kg after administration; P=0.004).

"Transgene-derived factor IX coagulant activity enabled the termination of baseline prophylaxis and the near elimination of bleeding and factor use," the authors write.

The study was funded by Spark Therapeutics and Pfizer.

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